I also wanted to add in my previous post not to trust the PM module too much. I use task manager/cores.
there is no doubt the PM module is fairly accurate seeing there is drop outs though but I never really trust it 100%.
you might be able to disable plug ins one by one to see if that is what might be spiking the core #1.
however it is odd, it worked in X3 without any problems but not in platinum. disk streaming throughput is a possibility but again, not an issue in X3. so im running out of suggestions for you Ping

my apology's wish I could be more of help.
maybe a possibility the VST scanning directory's are different ?
that would cause sonar to reach for a vst 32X vs a vst 64X ?